The prior art teaches a variety of systems for diagnosing operating parameters of an internal combustion engine. One such operating parameter is cylinder misfire. When a cylinder misfires, incomplete combustion occurs and uncombusted fuel is typically introduced into the exhaust system. Additionally, a misfiring cylinder degrades engine performance and efficiency.
U.S. Pat. No. 3,972,230, issued to Hanson et al., discloses an apparatus and method for detecting a malfunction in the cylinders of an internal combustion engine. While the engine is operated at an idle speed, power cycle time periods between successive ignition time are measured to obtain the deceleration rates between successive time periods. Average deceleration rates for the respective cylinders are computed and misfires occurring randomly in the cylinders are detected when individual deceleration rates exceed the average deceleration rates for the corresponding cylinder by a predetermined limit amount.
Other United States patents relating generally to the detection of cylinder misfire or other cylinder malfunctions include U.S. Pat. No. 4,179,922 issued to Bouverie et al., U.S. Pat. No. 4,930,479 issued to Osawa et al., U.S. Pat. No. 5,041,980 issued to Maddock et al., U.S. Pat. No. 5,044,195 issued to James et al., U.S. Pat. No. 5,056,360 issued to Dosdall et al. and U.S. Pat. No. 5,109,695, issued to James et al.
Some engine control systems utilize data from a sensor that cooperates with a wheel, having a plurality of teeth, which is used for detecting engine position in an engine cycle. Existing misfire detection strategies, however, are limited by the operating conditions during which misfire can be detected. For example, misfire detection is difficult during high speed, no-load operating conditions because of, among other reasons, the production inaccuracies of the multi-toothed wheel. One technique for correcting such inaccuracies is shown in U.S. Pat. No. 5,117,681, issued to Dosdall et al. This technique, however, requires a special measurement procedure.